Category: Endurance Training

Try Sprint Interval Training To Improve Your Running Performance

You have been hitting the trails, logging miles and doing everything that you are supposed to in order to improve your endurance and power.  Maybe you have a race coming up in a few weeks or you just want the personal accomplishment of getting through your regular run a little bit faster.  If you are finding that despite all your worthwhile efforts your performance has not changed in a meaningful way perhaps it is time to consider integrating sprint interval training into your program.

This week we take a look at an interesting study that shows a way for well trained individuals to really move the needle on their running performance with a minimal amount of time spent training.  As we go through the study keep in mind three things.  First, this study was conducted with subjects who were already well trained athletes.  We would expect to see positive changes in studies that take subjects who aren’t active and put them on aerobic/endurance/power based training plans.  If you are starting from a low level of fitness and get on a regular, supervised program most people will see a change for the better.  Taking a group of well trained athletes and coaxing a meaningful change in their performance is much more difficult and demonstrates the power of the training intervention.

Second, this study was done in a real world setting, not in a laboratory.  Often the changes that can be achieved in a very controlled setting working on a treadmill or cycle ergometer cannot be replicated in quite the same way in a real world setting.  If you cannot go out to the track, trail, road or gym and achieve the benefit of the specific plan studied then it might not matter all that much that it can produce an effect in the laboratory.

Third, this study achieved meaningful results with just a two week intervention.  Often we need data over much longer periods of time, weeks, months, even years to determine the impact of a particular intervention.  In the case of this study part of what was so interesting is that the trained athletes used as subjects achieved the beneficial effects of the sprint interval training program in just two weeks.  Who doesn’t want to do something that will improve their performance in such a short period of time?

The Study

In this study running performance was measured with a 3,000 meter time trial and a run timed to exhaustion at 90% of maximal aerobic speed (MAS).  The training program consisted of three workouts per week for two weeks.  In each workout the sprint intervals were 30 second all-out shuttle runs followed by 4 minutes of rest.  The subjects performed 4 rounds in their first workout, 5 rounds in their second, 6 rounds in their third and fourth workout, 7 rounds in their fifth workout and dropped down to 4 rounds in their sixth workout.

The total sprinting time over the two weeks totaled 16 minutes.  The entire 6 sessions only took 110 minutes including the rest time.  The shortest workout was 14 minutes and the longest was only 27.5 minutes.

To conduct the actual sprints, cones were placed every 5 meters for a 30 meter distance.  During the sprints the subjects would run to the 5m cone and back, then the 10m cone and back and so on until they reached the 30m distance.  They would continue running at full speed until the 30 seconds were up.

Three additional variables were also measured for each session.  1) The subjects peak power, which was considered the longest distance they ran in a 30-second period.  2) Mean power which was the total distance they ran for the session divided by the number of sets they ran that workout.  3) Fatigue index was considered the difference between the longest sprint they ran in any given workout and the shortest sprint they ran in the same workout.

Results

Maximal aerobic speed saw a 2.8% increase.  This was significant though the effect size was small.  For the timed run at 90% of maximal aerobic speed there was a 42% improvement (158.9 seconds) which was considered a large effect size.  The timed 3,000 meter run saw a decrease of 50.4 seconds which is a 5.7% improvement in time.  The effect size is considered small-to-medium.

Peak power had a 2.4% improvement (3.06 m), significant but a small-to-medium effect size.  Mean power had a significant 2.9% improvement (13.9 m) for a medium effect size.  The fatigue index showed a positive trend with a medium effect size thought it did not reach a level of statistical significance.

Putting It All Together

So what does this all mean for most runners out there?  First and most importantly it shows that a very short 2-week low volume program can produce significant improvements in performance.  Most competitive runners already have fairly lengthy training programs and a schedule of competitions to plan around.  Even if you are not a competitive runner odds are that you still have a limited amount of time to train and are still interested in improving your performance.  A simple low volume, high-intensity program like this can quickly make positive improvements in both endurance and anaerobic performance.  Additionally this study demonstrates that the improvements are not limited to untrained subjects that will respond to just about any regular training protocol, already highly trained subjects can make significant improvements with this type of training.

Secondly a program like this does not require any special equipment.  A few cones make it look pretty but some water bottles, t-shirts, a big rock all work equally as well.  It is always nice to have a new training technique that doesn’t require you to open your wallet.  This study clearly showed that the results can be achieved in a real world setting without highly calibrated expensive laboratory equipment.

Third, all you need is a clear 30 meter space to run your sprints.  This means it can be done almost anywhere.  Even if you don’t have a full 30 meters you could still follow the program and simply limit the longest available distance to 20 or 25 meters.  Even if you have to train indoors because of weather it is still simple to perform a program like this.

Fourth, it is easy for multiple athletes to perform this program at the same time.  Individuals can set up right next to each other.  This makes it ideal for those working with teams to put everyone through the program together.  There is the added benefit that running against others often motivates people to push even harder.

A program similar to this can also be used as a tapering plan allowing for high intensities and low volumes to be programmed as you get closer to competition.

So why does such a short duration, low volume program produce such good results?  The leading theory is that this high intensity training technique leads to increases in enzymatic activity in both the aerobic and anaerobic energy systems.  It is also possible that this approach improved neuromuscular capacity which can result in improved running economy.

The use of shuttle runs was an interesting choice of the authors.  It allowed for high intensity training while ensuring that the improvements seen in the actual tests were not the result of skill acquisition but due to physiological adaptations.  As previously mentioned it also allowed for a small space to be utilized and a competitive atmosphere to be established between subjects.    This leads to the question of if another form of sprint interval training could produce similar results?  There is probably nothing magical about the use of shuttle runs in and of themselves.  The high intensity that they stimulate is most likely the key factor so it would not be reaching too far to assume that if the same intensity can be maintained for a full 30 seconds on a longer sprint, similar results would probably be achievable.  This eliminates the advantage of only needing a small space along with some of the mental variety that shuttle runs introduce but coaches shouldn’t feel limited to only using that one approach to including high intensity sprint intervals.

It would be interesting to compare the results of this study to slightly different training protocols. What would happen if you used a time different then 30 seconds for the sprints?  Do you need to go all the way up to 7 sets or can similar results be achieved if the volume is kept lower and only 4 or 5 intervals are used?  Would more intervals produce greater results or what happens if the program if followed for more than 2 weeks?  Like all studies, this one could had to choose a particular set of variables to use but the positive outcomes they produced makes you want to explore how those variables can be tweaked to produce even greater outcomes or optimize the time actually committed to the program.

There you go.  If you are looking for a way to improve running performance but do not have hours to commit over a prolonged period of time now you have a technique that will allow you to turbo-charge your training with a simple to perform, short duration low volume sprint interval plan.  Who doesn’t want to see a 42% improvement in their paced running and a 5.7% improvement in their race time for such a small amount of training?

Koral, J., Oranchuk, D., Herrera, R. and Millet, G. (2018) Six Sessions Of Sprint Interval Training Improves Running Performance In Trained Athletes.  Journal of Strength and Conditioning Research. 32(3): 617-623.

Yes You Can Reverse The Effects On Your Heart Of Being Sedentary And Middle-Aged

When I was a younger trainer the only things that mattered for me as an individual in the gym as well as in my program design for clients was developing strength, adding muscle and burning off body fat.  Two and a half decades later those are still the primary things that clients are interested in focusing on and what I spend most of my time helping people address, however as I embrace middle age other important aspects of health and fitness are becoming more of a concern.  For myself and for my clients.

I was always a strength oriented athlete, and I use the words strength and athlete loosely.  I was neither particularly skilled athletically or strong until I found the gym.  In the weight room I found an environment where I was able to excel and use my particular build to great advantage.  If something involved moving heavy weights I was all over it.  Aerobically oriented sports were never my forte.  I recognized the importance of cardiovascular fitness and programmed those components for my clients but it was never the focus.  Without question the only ones who did their cardio were those who were excessively focused on body composition and burning calories.

These days I find myself thinking about the risks of heart disease, the decreases in athletic performance and the capacity to perform everyday physical activities that clients are encountering.  How to maximize risk reduction for diabetes, cancer, stroke and a myriad of other life limiting conditions.  More than ever I wish my clients would make time to exercise, specifically aerobic exercise that trains their cardiovascular systems.  Recently I came across an outstanding study that not only reinforced my concerns about this topic but also demonstrated the impact that regular, consistent aerobic exercise has on significantly reducing the impact of aging and a sedentary lifestyle.  One of the most important pieces of the study is the amount of exercise that is necessary to achieve what literally are time reversing impacts on our hearts.

Put Some Heart In It

Our left ventricle is responsible for pumping oxygenated blood to the rest of the body.  In a healthy heart, as blood fills the left ventricle it increases the stretch on the muscle tissue that forms the ventricle. This stretch on the muscle tissue results in a stronger contraction.  If an increased amount of blood is pumped into the left ventricle the stretch on the muscle tissue is even greater and the resulting contraction is greater.  This means even more blood is pumped from the heart to the rest of the body.  We refer to the amount of blood that is pumped from the heart with each beat as the stroke volume.  Being able to increase the stroke volume, pump more blood, during activity is generally a good thing.

If less blood fills the left ventricle there is less stretch on the muscle tissue and the result is a weaker contraction.  This means less blood is then pumped from the heart, a lower stroke volume.  So anything that causes less blood to fill the left ventricle between each beat or reduces the force with which the ventricle contracts is detrimental.

Now for the bad news, as we age the left ventricle tends to get stiffer.  This results in a decrease in the amount of blood that can fit in the chamber.  This is a problem because it means there is less blood available to be pumped out.  The reduced amount of blood also places less stretch on the muscle tissue resulting in a weaker contraction.  As we just learned these two things result in a lower stroke volume.

Not only do we see a reduction in stretch on the muscle tissue because of the reduced amount of blood in the ventricle, we also see a reduction in stretch on the muscle tissue because the muscles themselves have become stiffer and thicker.  Unlike skeletal muscles where thicker means stronger, with cardiac muscle tissue thicker does not necessarily always mean better.  So essentially there are now three factors resulting in a lower stroke volume; less blood filling the chamber and available to pump out, less stretch on the muscle tissues because of the reduced amount of blood resulting in a weaker contraction and less stretch on the heart muscle because it has become stiffer and thicker.  In a nutshell, aging sucks for our hearts, far more so if you are sedentary.

By the time someone reaches their senior years (65+) if they have been sedentary, adding in moderate aerobic exercise is not very effective in reversing the stiffness that is found in the left ventricle (Don’t stop exercising seniors.  Exercise is still effective through other mechanisms).  By contrast, masters athletes that have engaged in a lifetime of physical activity tend to show hearts that appear and function as they would in much younger individuals (Arbab-Zadeh et al 2004).  While it might not be reasonable to expect everyone to exercise at the same volume and intensity of competitive athletes, 4-5 days a week of regular exercise over a lifetime does appear to provide most of the benefits (Bhella et al. 2014).

Researchers have determined that this stiffening process begins in and can be identified in middle age (Fujimoto et al. 2012).  This led researches to question if they could provide an intervention in sedentary middle age individuals that would stop, limit or reverse the negative changes seen in the heart.

The Study Details

Howden et al. (2018) theorized that if they took a group of sedentary middle-aged individuals and put them on an exercise program performed 4-5 days a week consisting of cardiovascular exercise performed for at least 30 minutes, including 1-2 high intensity interval training sessions, they could prevent left ventricular stiffening.

There are four main reasons we should consider this a higher quality piece of research.  First, it was a prospective study.  Subjects were put on an intervention and then the results were measured instead of the majority of similar research that is retrospective in nature, meaning they take a current population and look back at what they report they did in the past and try to determine to what extent their prior behavior contributed to their current status.  Secondly the study also included a parallel control group whose activity was supervised and their results directly compared to the intervention group. Third, the study was randomized.  Once subjects were determined to be eligible for the study they were randomly assigned to either the intervention group or the control group.  Fourth, the study lasted for two years.  Prospective studies are very complicated to conduct and most similar types of research in this area are of much shorter duration.  Usually to have a longer term measurement of cardiovascular impacts retrospective studies are performed.  In addition, throughout the entire two years the variables in question were controlled in both groups

Ultimately sixty-one healthy middle-aged (45-64 years) individuals were chosen.  Anyone who reported a history of regular exercise was excluded.  Fifty-two subjects completed the study, 28 in the exercise group and 24 in the control group.  These numbers were determined to be large enough to make the results of the research statistically significant.  The subjects in the experimental group had a slow ramp up of their exercise volumes and intensities.  For the first month of the study the subjects in the experimental group performed three 30 minute cardio sessions per week at a base rate that was 1-20 beats below their maximum steady state heart rate.  In the second month 2 sessions were added where the subjects trained at their maximum steady state.  In month three a third session at maximum steady state was added.  In month 3 the subjects also began to perform high intensity intervals at 90-95% of their peak heart rate.  They performed a 4 minute interval followed by 3 minutes of recovery at 60-75% of peak heart rate.  Four rounds of the intervals were performed.  The day following high intensity intervals the subjects had a recovery day where they did 20-30 minutes of walking or light aerobic activity.

By month 6 the experimental group was training 5-6 days per week which included 2 interval sessions, 1 long training sessions of at least an hour and one 30 minute session at their base pace.  This program was maintained for 4 months.  At this point, after 10 months subjects were retested to adjust their training zones and they began a 14 month maintenance phase.  In this phase they only performed intervals 1 time per week.  The subjects were allowed to utilize different pieces of exercise equipment (bike, treadmill, elliptical, rower) or exercise outdoors (running, cycling, swimming) and were encouraged to perform different types of exercise to make the sessions fun and avoid injuries.  They were also instructed to perform strength training 2 times per week.

The control group was instructed to perform yoga, balance and strength training 3 times per week for the entire 2 years.  They were not allowed to perform any endurance exercise.  Both groups were closely monitored throughout the entire 2 years.

Results

Over the course of the first 10 months of the study the experimental group saw their maximum oxygen uptake (VO2max) increase by 18%.  This increase was then maintained over the following 14 months of the maintenance phase.  The control group actually saw their VO2max decrease by 1% over the course of two years as would be expected in untrained individuals as they get older.

Left ventricular end-diastolic volume (LVEDV) is a measure of the amount of blood that is in the left ventricle when it finishes its relaxation phase, right before it contracts.  More blood in the chamber means the surrounding heart muscle tissue is more pliable, stretching more to allow the increased volume.  This signifies a less stiff left ventricle and will result in higher stroke volumes because more blood is available to be pumped.  The experimental group saw a 17% increase in LVEDV over the initial 10 months of training.

Other direct measures of stiffness and pressure-volume relationships all showed a marked improvement in the experimental group.  The experimental group also saw a five beat drop in their resting heart rate while the control group did not experience any change.

Putting It All Together

The primary take away from this study is that 2 years of exercise for 30 minutes, 4 to 5 days a week including at least 1 day of higher intensity interval training results in significant reductions in left ventricle  and overall myocardial stiffness.  This can be directly related to decreases in the risks of cardiovascular disease.  This exercise protocol is exceptionally similar to recommendations offered by the American Heart Association and The American College of Sports Medicine.  Both promote 150 minutes of moderate exercise per week performed over 5 days per week for 30 minutes per day or vigorous exercise performed 3 days per week for at least 25 minutes.

The combination of low, moderate and high-intensity exercise also showed marked improvements in measures of fitness (VO2max and resting heart rate) that are also correlated with decreased cardiovascular risk.  The authors theorize that the higher intensity component of the program is a particularly powerful driver of the changes seen in these fitness related measures.

For those readers who have been riding their desk and sofa for far too long, the study also showed that these changes can take place in sedentary middle aged individuals and that this population does have the psychological capacity to adhere to a long term, regular exercise program.  If you haven’t been a lifelong athlete or regular exerciser there is now evidence that as an average middle-aged individual you can significantly improve the condition of your heart, lower your risk of heart disease and death and achieve higher levels of fitness.

Arbab-Zadeh, A., Dijk, E., Prasad, A., Fu, Q., Torres, P., Zhang, R., Thomas, J.D., Palmer, D. and Levine, B. (2004) Effect of Aging and Physical Activity on Left Ventricular Compliance, Circulation, Sep:110(13): 1799-1805

Bhella, P., Hastings, J., Fujimoto, N., Shibata, S., Carrick-Ranson, G., Adams-Huet, B. and Levine, B. (2014) Impact of Lifelong Exercise “Dose” on Left Ventricular Compliance and Distensibility. J Am Coll Cardiol. Sep 23: 64(12): 1257-1266

Fujimoto, N., Hastings, J., Bhella, P., Shibata, S., Gandhi, N., Carrick-Ranson, G., Palmer, D. and Levine, B. (2012) Effect of ageing on left ventricular compliance and distensibility in healthy sedentary humans. J Physiol. Apr 15: 590(pt 8): 1871-1880.

Howden, E., Sarma, S., Lawley, J., Opondo, M., Cornwell, W., Stoller, D., Urey, M., Adams-Huet, B. and Levine, B. (2018) Reversing the Cardiac Effects of Sedentary Aging in Middle Age-A Randomized Controlled Trial. Circulation. 117.030617. doi: 10.1161/CIRCULATIONAHA.117.030617. [Epub ahead of print]